JVET_M0068_M0171_MMVD_CLEANUP
Integrate JVET-M0068 and M0171.
- Remove flip and reuse MV scaling to scale MVD directly (same aspect as JVET-M0068)
- Fix zero candidate depending on slice_type, i.e. P-slice or B-slice
- Move bi-to-uni conversion after the MMVD candidate list construction
- in software, add bi-pred restriction at the end of setMergeInfo() and setMmvdMergeCandiInfo() rather than after getInterMergeCandidates().